Both MMORPG.com and BonusStage have tossed up reviews for NCsoft and Cryptic Studios' City of Villains. The guys at MMORPG.com have given it a 8.0/10:

One of the big draws for City of Villains is that casual and hardcore friends can play at their own speed and still hang out and run missions together. This is made possible by the lackey system (the equivalent to City of Heroes' sidekick system), which allows lower level players to lackey to a higher level friend, or lets higher levels malefactor down to the level of their friend (the former being the more popular and profitable option). While in range of their partners, lackeys have the fighting ability of a character one level lower. i.e. if a 5th level character lackeys to a 20th level character, the 5th level character will fight like an 19th level character. While the lackeys aren't as proficient as a normal 19th level character they have less skills, their enhancements aren't upgraded, etc they are able to contribute to the mission and receive rewards of experience and enhancements suitable to their level, as well as experience and salvage. Malefactors are lowered to the level of their partners, losing all their higher level skills though keeping their enhancements and enhancement slots. While partnered, malefactors don't get experience, but they do get extra infamy and can work off debt.

I was looking at City of Villains to fix many of the problems that plagued last year's City of Heroes. Unfortunately it was not able to do so and as a result, many of the positives and negatives of that title transferred to this. Though the super hero genre of MMORPGs is definitely a deviation from the usual medieval/fantasy styles that we've become accustomed to, whether or not you'll enjoy this game is largely dependant on whether or not you cared for City of Heroes. In the end though, this title is great introduction for those players hitting the MMO scene for the first time.